Drum type magnetic separator



June 27, 1967 T. E. MORTSELL 3,327,852

DRUM TYPE MAGNETIC SEPARATOR Original Filed April 12, 1955 I i Q2 UnitedStates Patent 3,327,852 DRUM TYPE MAGNETIC SEPARATOR Tage EmanuelMortsell, deceased, late of Stockholm, Sweden, by Gunnar Ahlstrom,administrator, Gavle, Sweden, assignor to Sala MaskinfabrilrsAktiebolag, Sala, Sweden, a corporation of Sweden Continuation ofabandoned application Ser. No. 590,963, Apr. 12, 1955. This applicationDec. 18, 1964, Ser. No. 419,614

4 Claims. (Cl. 209-219) This is a continuation of application Ser. No.500,963, filed Apr. 12, 1955, now abandoned.

The present invention relates to separators for separating magnetic andnon-magnetic granular materials from a mixture of such materials in adry state. More particularly the invention relates to the separation ofgangue from ores by a magnetic separator.

One object of the invention is to provide a magnetic separator of thetype referred to in which, particularly with respect to certain ores,renders a high capacity and an effective separation of the ganguepossible.

Another object of the invention is to provide a magnetic separator, inwhich the granular materials to be separated are exposed to a mutualmovement under frictional engagement on the surface of a drum under theinfluence of the magnetic force, whereby the separation of the materialsfrom one another is facilitated.

A further object of the invention is to provide, in a magnetic separatorhaving a roller with closely spaced permanent magnets and a drumsurrounding said roller to receive the mixture to be separated, meansenabling rotation of the roller and the drum in mutually oppositedirections or in the same direction or rotation only of the drum, whilemaintaining the roller stationary.

A still further object of the invention is to facilitate separation ofnon-magnetic material from the magnetic material in a mixture of suchmaterials by aid of closely set permanent magnets with a high fieldstrength.

The closely set permanent magnets may be made with a high fieldstrength, and the alternating polarities and the high speed at which thematerial is entrained by the drum brings about a particularly rapidmutual movement of the grains (threshing) on the envelope surface of thedrum, which promotes the separatiton of the non-magnetic grains in aneffective manner. In this process it is possible to apply acomparatively thick layer of material on the drum while maintaining theseparating capacity. It has been found that the separator is alsocapable of separating not completely crushed ore grains, so-calledhalf-grains, which may thus be separated and re-ground to a pure oreconcentrate.

The invention is further elucidated by an example of embodimentillustrated in the accompanying drawing by way of diagrammaticrepresentation, and in which FIGS. 1 and 2 show a dry separatorconstructed according to the invention in two vertical, partly-sectionedprojections at right angles to each other;

FIG. 3 is a transverse vertical section of a modification, and

FIG. 4 is a diagrammatic view illustrating the close spacing of themagnets.

Mounted in the frame 1 is a hollow shaft 2 having a magnet roller 3secured to one end thereof. The magnet roller consists of a hub 4 and ofpermanent magnets 3 ,327,852 Patented June 27, 1967 lad secured therein,said magnets being arranged radially and with their out-turned ends withalternating polarities, that is to say, that a north pole is followed bya south pole, counted along the peripheral portion of the roller.

Mounted in the hollow shaft 2 is a shaft 6 carrying a drum 7 made fromnon-magnetic material splined thereto, the non-magnetic materialconsisting of stainless steel, for example. The envelope surface of thedrum extends with a small clearance round the magnet roller 4 along theperipheral portion of the latter.

By means of a driving contrivance, shown as a pulley 8 on the shaft 6, ahigh rotational speed may be imparted to the drum 7. The magnet roller 3may be driven in the same direction but at a lower speed, and for thispurpose there is provided a gearing consisting, for example, of a gearwheel 9 secured to the pulley 8 and meshing with a smaller gear wheel 1tsecured on an intermediate shaft 11, which also has secured thereon astill smaller gear wheel 12 in engagement with a larger gear wheel 14secured to the shaft 2 of the magnet roller. The intermediate shaft isrotatably but non-displaceably mounted on a slide rod 15 pertaining toan operating contrivance carried by the frame, by means of whichcontrivance the wheels 10, 12 of the intermediate shaft may be broughtinto or out of engagement with the gear wheels 9 and 14.

At 16 is shown a device for the supply of a mixture of magnetic andnon-magnetic granular material, and 17 denotes a collection contrivancein the form of a casing for the separated non-magnetic material; 18designates a collecting device provided with a funnel and a containerfor the magnetic material. A rotating prong roller 19 may be provided toremove the magnetic material from the drum in the known manner, afterthe nonmagnetic material has been separated.

The mode of operation of the magnetic separator may be generally statedas follows:

The mixture of magnetic and non-magnetic pulverulent material to beseparated is supplied through the device 16 and falls down onto theenvelope surface of the drum 7 in a relatively thick layer. The magneticmaterial is retained by the magnets, and accordingly as the drum movesrelatively to the magnets, the grains of the material are brought intomovement relatively to each other so as to rub against one another, thenon-magnetic material in the layer then travelling outwardly to behurled out from the drum through the influence of the centrifugal force,this material then being collected in the collecting contrivance 17. Themagnetic material is entrained to the removing roller 19, where it isremoved from the drum and collected in the known manner.

With respect to the high peripheral speed of the drum 7 required by thecentrifugal separation, it will be preferable, at least for certainkinds of materials, to cause the magnet roller to rotate in the samedirection as the drum but at a lower speed than the latter, in whichcase the gearing 9 to 14 is thrown in, so that the movement of themagnet roller is obtained from the pulley 8 over the gear wheels 9, 1t),11 and 14 and the shafts 11 and 2.

The magnet roller may also be stationary, and in such case theintermediate shaft 11 is displaced to the right in FIG. 1 by means ofthe operating contrivance 15, so that the gear wheels 10 and 12 are outof engagement with the gear wheels 9 and 14.

With a stationary magnet roller or frame, the prong roller mightoptionally be omitted, the magnet roller then being without magnetsalong a portion of its circumference. The magnetic grains will thenleave the drum, as soon as they have been brought by the latter out ofthe magnetic field, that is to say, to the region of the gap between themagnets. This modification is illustrated in FIG. 3, in which 3designates the stationary magnet frame carried by a hub 4 and carryingpermanent mag nets 5' with alternating polarity mounted along a portionof the periphery, a gap having no magnets being provided over a sectionin advance of the topmost point of the rotary drum 7 where the materialto be separated is supplied through the feeding device 16. The materialis delivered to the device 16 by a hopper 16'. A collecting housing 21comprises three compartments, one 22 for the non-magnetic material, thesecond 23 for an intermediate product and the third! 24 for magneticmaterial of the highest concentration (purity). The attracted materialwhich has not been discharged from the rotating drum 7 by centrifugalaction will leave the latter substantially at the point 25, where theattraction by the magnets ceases. The material in the compartments dropsthrough bottom outlets 26, 27 and 28, respectively. A baffie plate 29pivoted at 30 between the compartments 22 and 23, and a similar baffleplate 31 pivoted at 32 between the compartments 23 and 24 may be set invarious positions as indicated by the arrows 33 to vary the ratiobetween the portions of the material which is discharged from the drum 7and collected in the compartments 22, 23 and 24.

An important feature of this invention resides in the close spacing ofthe magnets, or more specifically, the pitch of the magnets counted onthe periphery of an imaginary cylinder co-axial with the surroundingdrum or with the center of the support for the magnets. The pitch inthis connection is equal to the distance between the centers of theout-turned end surfaces of two arbitary adjacent magnets and isillustrated in FIG. 4. In this view of the drawings, p indicates thepitch, m. indicates the magnets and c represents an imaginary cylindercontacting with the out-turned ends of the magnets. A large number ofpole alterations are of importance for a complete separation of the finegrained materials. That is, the materials being separated should bemoved by the drum past as many poles as possible. The particles of thematerial being under separation are indicated on the external surface ofthe drum :1 which rotates around the magnet system. The particles formchains in the magnetic field and opposite to the space between adjacentmagnets the particles chains protrude as indicated at 6. It has beenfound that a great number of these protruding chain groups are ofimportance for the separation since the material moves and turns as thedrum surfaces passes the magnets and this facilitates the discharge ofthe nonmagnetic grains.

In the two examples herein mentioned, the maximum pitch indicated ismillimeters. In the first example reference is made to a separatorhaving a diameter of 400 millimeters and 48 poles as well as a gapcorresponding to 6 magnets or 12 poles. The total number of poles isthus 60, and a pitch diameter of a 400 millimeter cylinder is:

In the further example:

The maximum pitch indicated in the above examples is thus 45 and thisarrangement is important to the best functioning of the apparatus.

The invention is not restricted to the embodiments shown and described,this embodiment only referring to an example having for its object tofacilitate an understanding of the invention. If necessary, theseparation of fine powder may be facilitated by an air jet directedagainst the drum.

Having thus described an embodiment of the invention, it is obvious thatthe same is not to be restricted thereto, but is broad enough to coverall structures coming within the scope of the annexed claims.

What is claimed is:

1. A magnetic separator for mixtures of magnetic and non-magnetic drygranular materials comprising, a stationary magnet support, a pluralityof permanent magnets mounted in close proximity to one another on saidsupport with their out-turned ends located in an imaginary cylindersurface, the pitch of the magnet ends in said surface consisting of theperipheral distance between the centers of the magnets, being a maximumof 45 millimeters, the out-turned end of one magnet having diflerentpolarity as compared with the out-turned ends of adjacent magnets, adrum peripherally surrounding the magnets, said drum being co-axial withsaid imaginary cylinder surface, means for supplying the mixture to thetop of the drum and at a point located above the magnets, and means forrotating the drum at a peripheral speed sufficient to remove thenon-magnetic material from the drum through the action of thecentrifugal force.

2. A magnetic separator for separating magnetic material from a mixtureof magnetic and non-magnetic dry granular material comprisng, astationary magnet support, a plurality of permanent magnets mounted inclose proximity to one another over a substantially cylindrical part ofsaid support in substantially radial positions, said cylindrical partbeing at least degrees and beginning substantially at the top of thesupport, the outer ends of the magnets having their end surfaces locatedon an imaginary cylinder surface and being alternately of differentpolarity, the pitch of the pole surfaces having a maximum magnitude of45 millimeters, a drum co-axial with said cylinder surface andperipherally surrounding the magnets, means for supplying the mixture tobe separated to the periphery of the drum at the top of the same, andmeans for rotating the drum at a peripheral speed suflicient to causerelease of the non-magnetic material from the drum through the action ofthe centrifugal force while permitting the magnetic material to beretained on the drum for subsequent removal therefrom.

3. A magnetic separator for separating magnetic material from a mixtureof magnetic and non-magnetic material comprising, a stationary magnetsupport, a plurality of permanent magnets mounted in close proximity toone another over a cylindrical part only of the circumference of thesupport in substantially radial positions, the outer ends of adjacentmagnets having different polarities and being located in an imaginarycylinder surface, a drum peripherally surrounding said magnets, thepitch of the magnets ends in said surface being a maximum of 45millimeters, means for supplying a mixture to be separated, said meanssupplying said mixture to the periphery of the drum at a point locatedsubstantially at the top of the drum and at which point the drum beginsits travel downwardly, means for rotating the drum at a peripheral speedsufficient to cause release of the nonmagnetic ma-terial from the drumthrough the action of centrifugal force while permitting the magneticmaterial to adhere to the drum, the support having a gap between itsmagnets beginning substantially at the top of the inside of the drum andending at a distance therefrom corresponding to the total pitch of atleast five magnets.

4. A magnetic separator as provided for in claim 3, wherein the supportand drum are contained in a housing having a lower portion arrangedbelow the support and drum, said lower portion being divided into a plurality of separate outlets past which the drum is successively rotated,one of the outlets receiving non-magnetic material from the drum, and asecond outlet receiving 5 magnetic material, the latter outlet being sopositioned relative to the gap between the magnets that by movement ofthe magnetic material by the drum out of the magnetic field, and whichmagnetic field is interrupted by the gap, the magnetic material willfall from the drum and be received in the last-mentioned outlet.

References Cited UNITED STATES PATENTS 6 2,607,478 8/1952 Newton 2092192,698,685 1/1955 Newton 209-219 3,045,822 7/ 1962 Cavanagh 20921'9FOREIGN PATENTS 637,992 10/ 1936 Germany.

10 pages 913 and 914, John Wiley and Sons, Inc., NY.

HARRY B. THORNTON, Primary Examiner. R. HALPER, Assistant Examiner.

1. A MAGNETIC SEPARATOR FOR MIXTURES OF MAGNETIC AND NON-MAGNETIC DRYGRANULAR MATERIALS COMPRISING, A STATIONARY MAGNET SUPPORT, A PLURALITYOF PERMANENT MAGNETS MOUNTED IN CLOSE PROXIMITY TO ONE ANOTHER ON SAIDSUPPORT WITH THEIR OUT-TURNED ENDS LOCATED IN AN IMAGINARY CYLINDERSURFACE, THE PITCH OF THE MAGNET ENDS IN SAID SURFACE CONSISTING OF THEPERIPHERAL DISTANCE BETWEEN THE CENTERS OF THE MAGNETS, BEING A MAXIMUMOF 45 MILLIMETERS, THE OUT-TURNED END OF ONE MAGNET HAVING DIFFERENTPOLARITY AS COMPARED WITH THE OUT-TURNED ENDS OF ADJACENT MAGNETS, ADRUM PERIPHERALLY SURROUNDING THE MAGNETS, SAID DRUM BEING CO-AXIAL WITHSAID IMAGINARY CYLINDER SURFACE, MEANS FOR SUPPLYING THE MIXURE TO THETOP OF THE